Pressurized-water, boiling-water, and pressurized-gas nuclear reactors have a core in which considerable pressure is contained, as discussed in the commonly assigned U.S. Pat. No. 3,734,827 issued May 22, 1973 to Franz SCHILLING for a NUCLEAR-REACTOR STRUCTURE.
Bursting of such a core presents a grave peril for any persons or structure nearby. Not only can such cores burst or explode with considerable force, sending fragments outwardly at high speed, but they can project radioactive materials and liquids outwardly to render the surroundings unusably radioactive.
It is therefore necessary to provide for this possibility of bursting by surrounding the core with a shield which acts as a simple physical barrier between the core and the outside. As a general rule this has been accomplished through the simple, but expensive and bulky, expedient of casting thick concrete walls all around the core.
The core must be checked periodically for faults or developing cracks. To do this inspection it is necessary to pass an ultrasonic, transducer or the like over the surface of the core while taking readings to ascertain if its surface is in good condition. Thus it is necessary to provide an inspection cavity all around the core between it and the burst shield. For this reason it is necessary to build the shield stronger and thicker than would be necessary if it could lie directly against the outside of the core, since the outwardly projected fragments of a bursting core have a high kinetic energy.